1. Field of the Invention
The present invention relates generally to heating devices used for straightening hair, and it particularly refers to a heating plate included in hair straightening irons.
2. Description of Prior Art
As it is known, there are numerous applications which have been thought for the production of heating units equipped with a good electrical insulation, which ensure not only its safe handling but also the protection of the resistor from external agents.
In order to solve this problem, several solutions, based on protecting the electrical element, have been presented and submitted, such is the case of the ceramic resistors.
After a search, several productions have been found, among them, the following can be listed:
Patent WO 2006/081223, which relates to a “Method of manufacturing tin oxide-based ceramic resistors and obtained resistors”. There, it is explained how different steps are followed in the process of forming antimony powder with a dose of tin oxide and mixed with a pulverulent vitrifiable compound, and making the resistor by thermal treatment.
U.S. Pat. No. 4,804,823 which consists in a “Ceramic heater”. The heat generator is a resistor placed inside or over the surface of a ceramic holder, with terminals connected at both ends of the resistor. The ceramic substrate is made of certain nitrite selected from the group Si and Al, while the resistor is made of nitrite from Ti (TiN) and Tungsten Carbonate (WC).
U.S. Pat. No. 6,960,741 refers to a “Large area ceramic heater”. It describes a disk as a collector burner aimed for cooking, which is provided by two bowed parts of alumina ceramic having opposed concave regions adhered together as a laminate, between which the electrical resistor is deposited.
There are also other patents which are manufactured in different ways or are made of different materials. There have been found no interferences with the present invention, among the above-mentioned examples and other similar ones.